1. Field of the Invention
The present invention relates to an LC element capable of attenuating a predetermined frequency band and used either as part of a semiconductor or other device, or as a discrete element, a semiconductor device including such an LC element and a method for manufacturing such an LC element.
2. Background Art
The rapid advancement of electronics technology in recent years has brought about the use of electronic circuits in an increasingly broad range of fields. Therefore, stable operation of these electronic circuits is sought without being affected by external conditions.
However, electronic circuits are directly or indirectly subject to the incursion of external noise. Consequently, a problem exists whereby operating error is caused in electronic products using electronic circuits.
In particular, there are many cases of using switching regulators as electronic circuit DC power supplies. As a result of transient current produced by such operations as switching, or by load fluctuations arising from switching operation of utilized digital ICs, intense noise having many frequency components is often produced in the switching regulator power supply line. This noise is conveyed via the power supply line or by radiation to other circuits in the same product, giving rise to such effects as operating error and impaired signal to noise ratio, and in some cases even causing operating error in other nearby electronic products.
Various types of noise filters are presently being used with respect to electronic circuits in order to remove noise. In particular, since a great many electronic products of numerous types have come into use in recent years, the regulations against noise have grown ever more stringent, and development of an LC element having functions as a compact high performance noise filter capable of reliably removing such noise is desired.
One example of this type of LC element is an LC noise filter disclosed in Japanese Patent Application Laid-open No. 3-259608. In the case of this LC noise filter, the L (inductance) and C (capacitance) components exist as distributed constants, and compared to a lumped constant type LC filter, favorable attenuation response can be obtained over a relatively wide band.
However, manufacturing process of this LC noise filter is complicated because this LC noise filter is formed by folding an insulation sheet which has been provided with the conductor on both sides to form the inductor and the capacitor.
Also, wiring is required when directly inserting this LC filter into an IC or LSI power supply or signal line, thus necessitating time and labor for installing the components. In addition, since this LC filter is formed as a discrete component, inclusion in an IC or LSI circuit, i.e., insertion into the internal wiring of an IC, LSI or other device is nearly impossible.
Furthermore, in the case of this LC noise filter, since a capacitor formed in the manner of a distributed constant is determined by the respective shape and arrangement of the conductors which also functions as the inductors, after completion of the product, the capacitance is fixed. Consequently, the problem arises whereby the overall characteristics are also fixed and use for general purpose applications is restricted. For example, in order to change only the capacitance, the shape of the capacitor type conductor must be changed. Freely changing the capacitance of the LC noise filter which has been connected to a particular circuit according to requirements is difficult.